The in-situ detection of corrosion and failures represents an important stage in the procedures of maintenance of metallic structures. The use of nanotechnology embedded in the protective coatings is a promising way to develop user-friendly and cost-effective corrosion detection systems and has to be explored by the coating industry. Several groups have already reported the use of coating systems containing pH indicators and fluorescent probes to detect the corrosion of the substrates. The interest of encapsulating these indicators to prevent undesired interactions and leaching from the coating has also been argued.
In this work, layered double hydroxides (LDHs) are intercalated with hexacyanoferrate to be used as corrosion indicator coating additives. Their structure is characterized as well as their toxicity towards marine species. The nanocontainers are then dispersed in a coating matrix to detect the corrosion of a steel substrate at early stage. Electrochemical impedance spectroscopy measurements are performed to monitor the response of this coating towards immersion in corrosive medium. The reaction of the color indicator with the Fe3+ ions liberated during corrosion produces a stable blue precipitate coloring the coating, which could be detected by optical instruments to highlight the zones of failure in the structure.
In many applications using metallic parts, corrosion is a main drawback to the integrity of the structures, particularly offshore where humidity and salt lead to aggressive environments. Corrosion detection for maintenance of structures in specific field such as marine and offshore application is usually very complex and expensive,1 making it a domain eager for innovative technology allowing to reduce costs. In this context, the functionalization of the protective coatings appears to bring opportunities for direct in-situ corrosion detection. A trend in this field of research is the development of formulations containing color indicator changing state when corrosion is occurring under the protective coating, making it detectable by a simple visual inspection.
